1. Field of the Invention
The present invention relates to polyolefin compositions, and more particularly to compositions capable of being used for the manufacture of polyolefin film having so-called "cling" properties, "cling" being the term used to describe the ability of a film to stick or cling to itself without the use of an adhesive, heat treatment or the like.
2. Description of the Prior Art
Plastic films exhibiting cling properties are well known in the packaging trade. Such films are used in supermarkets, especially in North America, for the packaging of fresh meat. For instance selections of fresh meat, for example, beef or pork chops, ground or minced meat, poultry and the like, may be placed on a tray, for example a foamed polystyrene tray, and wrapped with a plastic film that has the ability to cling to itself. Cling film is also sold in roll form for use in households.
Plastic film has recently been used in the stretch wrapping of loaded pallets in which the pallets are spirally wrapped, on a rotating turntable, with film maintained under tension. The properties of the film must be such that the load on the pallet is protected and held in place during shipment. The use of a film with cling properties could permit automatic wrapping of loaded pallets without any need for the use of an adhesive.
Cling film used in supermarkets is usually a polyvinyl chloride film while that used in households may be polyvinyl chloride or polyvinylidene chloride film, the latter being used primarily because of its barrier properties. Polyolefin films, especially polyethylene films, have generally not been used in packaging applications requiring film with cling properties because they tend to lack adequate cling characteristics.
It is known to incorporate additives into polyethylene to provide the polyethylene with antistatic properties. Examples of such additives are N,N-bis(2-hydroxyethyl) alkylamine where the alkyl group is a C.sub.12 -C.sub.18 alkyl group and N-(3-dodecyloxy-2-hydroxypropyl) ethanolamine.